Don Savage
Headquarters, Washington, DC July 23, 1998
(Phone: 202/358-1727)
Ray Villard
Space Telescope Science Institute, Baltimore, MD
(Phone: 410/338-4514)
Mohammad Heydari-Malayeri
Paris Observatory, Paris, France
(Phone: 33-1-40-51-20-76)
RELEASE: 98-132
NEARBY STAR CLUSTER YIELDS INSIGHTS INTO EARLY UNIVERSE
NASA's Hubble Space Telescope has taken a "family portrait"
of young, ultra-bright stars nested in their embryonic cloud of
glowing gases. The celestial maternity ward, called N81, is
located 200,000 light-years away in the Small Magellanic Cloud, a
small irregular satellite galaxy of our Milky Way. These are
probably the youngest massive stars ever seen in the nearby
galaxy.
The nebula offers a unique opportunity for a close-up glimpse
of the "firestorm" accompanying the birth of extremely massive
stars, each blazing with the brilliance of 300,000 of our suns.
Such galactic fireworks were much more common billions of years
ago in the early universe, when most star formation took place.
"This is giving us new insights into the physical
mechanisms governing star formation in far away galaxies that
existed long ago," says Mohammad Heydari-Malayeri, who headed the
international team of astronomers who made the discovery using
Hubble's Wide Field and Planetary Camera 2.
Because these stars are deficient in heavier elements,
they also evolve much like the universe's earliest stars, which
were made almost exclusively of the primordial elements hydrogen
and helium that were created in the big bang. The Small
Magellanic Cloud is a unique laboratory for studying star
formation in the early universe since it is the closest and best
seen galaxy containing so-called "metal-poor" first- and second -
generation type stars.
These observations show that massive stars may form in
groups. "As a result, it is more likely some of these stars are
members of double and multiple star systems," says Heydari-
Malayeri. "The multiple systems will affect stellar evolution
considerably by ejecting a great deal of matter into space."
This furious rate of mass loss from these stars is evident
in the Hubble picture, which reveals dramatic shapes sculpted in
the nebula's wall of glowing gases by violent stellar winds and
shock waves. "This implies a very turbulent environment typical
of young star formation regions," Heydari-Malayeri adds.
He believes one of the members of the cluster may be an
extremely rare and short-lived class of super-hot star (50,000
degrees Kelvin) called a Wolf-Rayet. This star represents a
violent, transitional phase in the final years of a massive star's
existence - before it ultimately explodes as a supernova.
"If confirmed by future Hubble observations, this finding
will have a far-reaching impact on stellar evolutionary models,"
says Heydari-Malayeri. "That's because the Wolf-Rayet candidate is
fainter than other such stars in that galaxy, in contrast with the
predictions of these models." The team's work will be shortly
submitted for publication in the European journal Astronomy and
Astrophysics.
Hubble's resolution allows astronomers to pinpoint 50
separate stars tightly packed in the nebula's core within a 10
light-year diameter -- slightly more than twice the distance
between Earth and the nearest star to our sun. The closest pair
of stars is only one-third of a light-year apart. Before the
Hubble observations, N81 was simply dubbed, "The Blob" because its
features were indistinguishable by other telescopes.
The Space Telescope Science Institute is operated by the
Association of Universities for Research in Astronomy, Inc. for
NASA, under contract with NASA's Goddard Space Flight Center,
Greenbelt, MD. The Hubble Space Telescope is a project of
international cooperation between NASA and the European Space
Agency.
- end -
NOTE TO EDITORS: A photo and caption associated with this release
are available via the World-Wide Web at:
http://oposite.stsci.edu/1998/25